Since 1996, all light and medium duty vehicles manufactured for sale in North America have been equipped with an on-board diagnostic II (OBDII) system. The primary objective of the OBDII system was to reduce vehicle emissions via the real-time monitoring of engine function and emissions systems. All OBDII-equipped light/medium-duty vehicles use a Mass Airflow (MAF) and/or Manifold Air Pressure (MAP) sensors to provide real time input and feedback to the engine's fuel management system. The fuel management system is operated in real-time by one of the vehicle's Electronic Control Units (ECU), known as the Powertrain Control Module (PCM). In vehicles that are appropriately equipped, real-time sampled MAF and/or MAP sensor data can be requested from the PCM, via the OBDII diagnostic port. Either of these parameters can be used to calculate the fuel consumption of a vehicle.
Although there have been previous prior art attempts to determine vehicle's fuel efficiency, see e.g. U.S. Pat. Nos. 6,594,579 and 6,988,033 to Lowrey et al, the need still exists in the automotive industry for developing accurate and reliable methods for determining fuel consumption and fuel efficiency in vehicles.